scholarly journals Prefrontal attentional saccades explore space rhythmically

2019 ◽  
Author(s):  
Corentin Gaillard ◽  
Sameh Ben Hadj Hassen ◽  
Fabio Di Bello ◽  
Yann Bihan-Poudec ◽  
Rufin VanRullen ◽  
...  
Keyword(s):  
Space Exploration ◽  
Visual Space ◽  
List Type ◽  
Top Down ◽  
Frontoparietal Network ◽  
Rhythmic Cycles ◽  
Processing Accuracy ◽  
Alpha 7 ◽  
Sensory Encoding ◽  
Attentional Spotlight

SummaryRecent studies suggest that attention samples space rhythmically through oscillatory interactions in the frontoparietal network. However, the precise mechanism through which the prefrontal cortex, at the source of attention control signals, organizes this rhythmic exploration of space remains unknown. We show that, when decoded at a high spatial (0.1°) and temporal resolution (50ms), the prefrontal covert attentional spotlight, aka the mind’s eye, continuously explores space at an alpha 7-12 Hz rhythm. When sensory events are presented at a specific optimal phase (resp. anti-phase) with respect to this rhythm, sensory encoding and behavioral report are accurate (resp. poor). We propose that this rhythmic prefrontal attentional spotlight dynamics corresponds to a continuous overt exploration of space via alpha-clocked attentional saccades. These attentional saccades are highly flexible, their pattern of space exploration depending both on within-trial and across-task contingencies. These results are discussed in the context of exploration and exploitation strategies and prefrontal top-down attentional control.HighlightsThe decoded prefrontal attentional spotlight samples visual space in rhythmic cyclesThis rhythmic attentional exploration predicts neuronal sensory processing accuracyThis rhythmic attentional exploration predicts overt behavioral accuracyThese rhythmic cycles define alpha-clocked attentional saccadesSpace exploration by attentional saccades is highly flexible and under top-down control

scholarly journals Layer-dependent multiplicative effects of spatial attention on contrast responses in human early visual cortex

2020 ◽  
Author(s):  
Fanhua Guo ◽  
Chengwen Liu ◽  
Chencan Qian ◽  
Zihao Zhang ◽  
Kaibao Sun ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Spatial Attention ◽  
Middle Layer ◽  
Additive Effect ◽  
List Type ◽  
Strong Nonlinearity ◽  
Top Down ◽  
Contrast Gain ◽  
Early Visual Cortex ◽  
Deep Layers

AbstractAttention mechanisms at different cortical layers of human visual cortex remain poorly understood. Using submillimeter-resolution fMRI at 7T, we investigated the effects of top-down spatial attention on the contrast responses across different cortical depths in human early visual cortex. Gradient echo (GE) T2* weighted BOLD signal showed an additive effect of attention on contrast responses across cortical depths. Compared to the middle cortical depth, attention modulation was stronger in the superficial and deep depths of V1, and also stronger in the superficial depth of V2 and V3. Using ultra-high resolution (0.3mm in-plane) balanced steady-state free precession (bSSFP) fMRI, a multiplicative scaling effect of attention was found in the superficial and deep layers, but not in the middle layer of V1. Attention modulation of low contrast response was strongest in the middle cortical depths, indicating baseline enhancement or contrast gain of attention modulation on feedforward input. Finally, the additive effect of attention on T2* BOLD can be explained by strong nonlinearity of BOLD signals from large blood vessels, suggesting multiplicative effect of attention on neural activity. These findings support that top-down spatial attention mainly operates through feedback connections from higher order cortical areas, and a distinct mechanism of attention may also be associated with feedforward input through subcortical pathway.HighlightsResponse or activity gain of spatial attention in superficial and deep layersContrast gain or baseline shift of attention in V1 middle layerNonlinearity of large blood vessel causes additive effect of attention on T2* BOLD

scholarly journals Auditory attention alterations in migraine: a behavioral and MEG/EEG study

2019 ◽  
Author(s):  
Rémy Masson ◽  
Yohana Lévêque ◽  
Geneviève Demarquay ◽  
Hesham ElShafei ◽  
Lesly Fornoni ◽  
...  
Keyword(s):  
Event Related Potentials ◽  
Orienting Response ◽  
List Type ◽  
Top Down ◽  
Attention Task ◽  
Bottom Up ◽  
Attentional Processes ◽  
Related Potentials ◽  
The Right ◽  
Task Irrelevant

AbstractObjectivesTo evaluate alterations of top-down and/or bottom-up attention in migraine and their cortical underpinnings.Methods19 migraineurs between attacks and 19 matched control participants performed a task evaluating jointly top-down and bottom-up attention, using visually-cued target sounds and unexpected task-irrelevant distracting sounds. Behavioral responses and MEG/EEG were recorded. Event-related potentials and fields (ERPs/ERFs) were processed and source reconstruction was applied to ERFs.ResultsAt the behavioral level, neither top-down nor bottom-up attentional processes appeared to be altered in migraine. However, migraineurs presented heightened evoked responses following distracting sounds (orienting component of the N1 and Re-Orienting Negativity, RON) and following target sounds (orienting component of the N1), concomitant to an increased recruitment of the right temporo-parietal junction. They also displayed an increased effect of the cue informational value on target processing resulting in the elicitation of a negative difference (Nd).ConclusionsMigraineurs appear to display increased bottom-up orienting response to all incoming sounds, and an enhanced recruitment of top-down attention.SignificanceThe interictal state in migraine is characterized by an exacerbation of the orienting response to attended and unattended sounds. These attentional alterations might participate to the peculiar vulnerability of the migraine brain to all incoming stimuli.HighlightsMigraineurs performed as well as healthy participants in an attention task.However, EEG markers of both bottom-up and top-down attention are increased.Migraine is also associated with a facilitated recruitment of the right temporo-parietal junction.

scholarly journals Landmark-Centered Coding in Frontal Cortex Visual Responses

2020 ◽  
Author(s):  
Adrian Schütz ◽  
Vishal Bharmauria ◽  
Xiaogang Yan ◽  
Hongying Wang ◽  
Frank Bremmer ◽  
...  
Keyword(s):  
Frontal Cortex ◽  
Visual Space ◽  
List Type ◽  
Visual Response ◽  
Visual Responses ◽  
Visual Landmarks ◽  
Specific Target ◽  
Visual Coding ◽  
The Gaze ◽  
Landmark Configuration

SummaryVisual landmarks influence spatial cognition [1–3], navigation [4,5] and goal-directed behavior [6–8], but their influence on visual coding in sensorimotor systems is poorly understood [6,9–11]. We hypothesized that visual responses in frontal cortex control gaze areas encode potential targets in an intermediate gaze-centered / landmark-centered reference frame that might depend on specific target-landmark configurations rather than a global mechanism. We tested this hypothesis by recording neural activity in the frontal eye fields (FEF) and supplementary eye fields (SEF) while head-unrestrained macaques engaged in a memory-delay gaze task. Visual response fields (the area of visual space where targets modulate activity) were tested for each neuron in the presence of a background landmark placed at one of four oblique configurations relative to the target stimulus. 102 of 312 FEF and 43 of 256 SEF neurons showed spatially tuned response fields in this task. We then fit these data against a mathematical continuum between a gaze-centered model and a landmark-centered model. When we pooled data across the entire dataset for each neuron, our response field fits did not deviate significantly from the gaze-centered model. However, when we fit response fields separately for each target-landmark configuration, the best fits shifted (mean 37% / 40%) toward landmark-centered coding in FEF / SEF respectively. This confirmed an intermediate gaze / landmark-centered mechanism dependent on local (configuration-dependent) interactions. Overall, these data show that external landmarks influence prefrontal visual responses, likely helping to stabilize gaze goals in the presence of variable eye and head orientations.HighlightsPrefrontal visual responses recorded in the presence of visual landmarksResponse fields showed intermediate gaze / landmark-centered organizationThis influence depended on specific target-landmark configurations

Push-Pull Mechanism of Selective Attention in Human Extrastriate Cortex

2004 ◽  
Vol 92 (1) ◽  
pp. 622-629 ◽  
Author(s):  
Mark A. Pinsk ◽  
Glen M. Doniger ◽  
Sabine Kastner
Keyword(s):  
Selective Attention ◽  
Target Selection ◽  
Visual Space ◽  
Neural Representation ◽  
Extrastriate Cortex ◽  
Related Activity ◽  
Directed Attention ◽  
Frontoparietal Network ◽  
Visual Hemifield ◽  
Attentional Load

Selective attention operates in visual cortex by facilitating processing of selected stimuli and by filtering out unwanted information from nearby distracters over circumscribed regions of visual space. The neural representation of unattended stimuli outside this focus of attention is less well understood. We studied the neural fate of unattended stimuli using functional magnetic resonance imaging by dissociating the activity evoked by attended (target) stimuli presented to the periphery of a visual hemifield and unattended (distracter) stimuli presented simultaneously to a corresponding location of the contralateral hemifield. Subjects covertly directed attention to a series of target stimuli and performed either a low or a high attentional-load search task on a stream of otherwise identical stimuli. With this task, target-search-related activity increased with increasing attentional load, whereas distracter-related activity decreased with increasing load in areas V4 and TEO but not in early areas V1 and V2. This finding presents evidence for a load-dependent push-pull mechanism of selective attention that operates over large portions of the visual field at intermediate processing stages. This mechanism appeared to be controlled by a distributed frontoparietal network of brain areas that reflected processes related to target selection during spatially directed attention.

Neural Correlates of Divided Attention in Natural Scenes

2016 ◽  
Vol 28 (9) ◽  
pp. 1392-1405 ◽  
Author(s):  
Sabrina Fagioli ◽  
Emiliano Macaluso
Keyword(s):  
Real World ◽  
Divided Attention ◽  
Premotor Cortex ◽  
Natural Scenes ◽  
Multiple Streams ◽  
Top Down ◽  
Frontoparietal Network ◽  
Object Categories ◽  
Visual Hemifields ◽  
Spatial Locations

Individuals are able to split attention between separate locations, but divided spatial attention incurs the additional requirement of monitoring multiple streams of information. Here, we investigated divided attention using photos of natural scenes, where the rapid categorization of familiar objects and prior knowledge about the likely positions of objects in the real world might affect the interplay between these spatial and nonspatial factors. Sixteen participants underwent fMRI during an object detection task. They were presented with scenes containing either a person or a car, located on the left or right side of the photo. Participants monitored either one or both object categories, in one or both visual hemifields. First, we investigated the interplay between spatial and nonspatial attention by comparing conditions of divided attention between categories and/or locations. We then assessed the contribution of top–down processes versus stimulus-driven signals by separately testing the effects of divided attention in target and nontarget trials. The results revealed activation of a bilateral frontoparietal network when dividing attention between the two object categories versus attending to a single category but no main effect of dividing attention between spatial locations. Within this network, the left dorsal premotor cortex and the left intraparietal sulcus were found to combine task- and stimulus-related signals. These regions showed maximal activation when participants monitored two categories at spatially separate locations and the scene included a nontarget object. We conclude that the dorsal frontoparietal cortex integrates top–down and bottom–up signals in the presence of distractors during divided attention in real-world scenes.

scholarly journals Neural correlates of early sound encoding and their relationship to speech in noise perception

2016 ◽  
Author(s):  
Emily B.J. Coffey ◽  
Alexander M.P. Chepesiuk ◽  
Sibylle C. Herholz ◽  
Sylvain Baillet ◽  
Robert J. Zatorre
Keyword(s):  
Auditory System ◽  
Musical Training ◽  
Task Demands ◽  
List Type ◽  
Top Down ◽  
Feed Forward ◽  
Frequency Following Response ◽  
Language Functions ◽  
Speech In Noise ◽  
Complementary Role

AbstractSpeech-in-noise (SIN) perception is a complex cognitive skill that affects social, vocational, and educational activities. Poor SIN ability particularly affects young and elderly populations, yet varies considerably even among healthy young adults with normal hearing. Although SIN skills are known to be influenced by top-down processes that can selectively enhance lower-level sound representations, the complementary role and of feed-forward mechanisms and their relationship to musical training is poorly understood. Using a paradigm that eliminates the main top-down factors that have been implicated in SIN performance, we aimed to better understand how robust encoding of periodicity in the auditory system (as measured by the frequency-following response) contributes to SIN perception. Using magnetoencephalograpy, we found that the strength of encoding at the fundamental frequency in the brainstem, thalamus, and cortex is correlated with SIN accuracy, as was the amplitude of the slower cortical P2 wave, and these enhancements were related to the extent and timing of musicianship. These results are consistent with the hypothesis that basic feed-forward sound encoding affects SIN perception by providing better information to later processing stages, and that modifying this process may be one mechanism through which musical training might enhance the auditory networks that subserve both musical and language functions.Highlights–Enhancements in periodic sound encoding are correlated with speech-in-noise ability–This effect is observed in the absence of contextual cues and task demands–Better encoding is observed throughout the auditory system and is right-lateralized–Stronger encoding is related to stronger subsequent secondary auditory cortex activity–Musicianship is related to both speech-in-noise perception and enhanced MEG signals

scholarly journals Suggested visual blockade during hypnosis: Top-down modulation of stimulus processing in a visual oddball task

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0257380
Author(s):  
Marcel Franz ◽  
Barbara Schmidt ◽  
Holger Hecht ◽  
Ewald Naumann ◽  
Wolfgang H. R. Miltner
Keyword(s):  
Computing Time ◽  
Event Related Potentials ◽  
Source Analysis ◽  
Oddball Paradigm ◽  
Top Down ◽  
Time Frequency ◽  
Frontoparietal Network ◽  
Related Potentials ◽  
Visual Oddball ◽  
Hypnotic Suggestions

Several theories of hypnosis assume that responses to hypnotic suggestions are implemented through top-down modulations via a frontoparietal network that is involved in monitoring and cognitive control. The current study addressed this issue re-analyzing previously published event-related-potentials (ERP) (N1, P2, and P3b amplitudes) and combined it with source reconstruction and connectivity analysis methods. ERP data were obtained from participants engaged in a visual oddball paradigm composed of target, standard, and distractor stimuli during a hypnosis (HYP) and a control (CON) condition. In both conditions, participants were asked to count the rare targets presented on a video screen. During HYP participants received suggestions that a wooden board in front of their eyes would obstruct their view of the screen. The results showed that participants’ counting accuracy was significantly impaired during HYP compared to CON. ERP components in the N1 and P2 window revealed no amplitude differences between CON and HYP at sensor-level. In contrast, P3b amplitudes in response to target stimuli were significantly reduced during HYP compared to CON. Source analysis of the P3b amplitudes in response to targets indicated that HYP was associated with reduced source activities in occipital and parietal brain areas related to stimulus categorization and attention. We further explored how these brain sources interacted by computing time-frequency effective connectivity between electrodes that best represented frontal, parietal, and occipital sources. This analysis revealed reduced directed information flow from parietal attentional to frontal executive sources during processing of target stimuli. These results provide preliminary evidence that hypnotic suggestions of a visual blockade are associated with a disruption of the coupling within the frontoparietal network implicated in top-down control.

Combining Interactive Exploration and Optimization for Assembly Design

1998 ◽  
Vol 120 (1) ◽  
pp. 24-31 ◽  
Author(s):  
G. J. Kim ◽  
S. Szykman
Keyword(s):  
Simulated Annealing ◽  
Design Space Exploration ◽  
Design Space ◽  
Space Exploration ◽  
Explicit Representation ◽  
Top Down ◽  
Design Constraints ◽  
Overall Design ◽  
Assembly Design ◽  
Design Alternatives

This paper presents an integrated framework for conceptual assembly design. Because the complexity of assembly design leads to extremely large design spaces, adequate support of design space exploration is a key issue that must be addressed. CAMF allows the designer to manage the overall design process and explore the design space through explicit representation of design stages and their relationships (history), assembly design constraints, and rationale. The designer is free to use both bottom-up or top-down approaches to explore different assembly configurations. Exploration of the design space is further enabled by incorporating a simulated annealing-based refinement tool that allows the designer to rapidly complete partial designs, refine complete designs, and generate multiple design alternatives.

scholarly journals Visual cortical entrainment to unheard acoustic speech reflects intelligibility of lip movements and is mediated by dorsal stream regions

2018 ◽  
Author(s):  
A. Hauswald ◽  
C. Lithari ◽  
O. Collignon ◽  
E. Leonardelli ◽  
N. Weisz
Keyword(s):  
Visual Cortex ◽  
Acoustic Signal ◽  
Temporal Cortex ◽  
Dorsal Stream ◽  
List Type ◽  
Top Down ◽  
Entrainment Effect ◽  
Speech Envelope ◽  
Cortical Entrainment ◽  
Visual Cortical

AbstractSuccessful lip reading requires a mapping from visual to phonological information [1]. Recently, visual and motor cortices have been implicated in tracking lip movements (e.g. [2]). It remains unclear, however, whether visuo-phonological mapping occurs already at the level of the visual cortex, that is, whether this structure tracks the acoustic signal in a functionally relevant manner. In order to elucidate this, we investigated how the cortex tracks (i.e. entrains) absent acoustic speech signals carried by silent lip movements. Crucially, we contrasted the entrainment to unheard forward (intelligible) and backward (unintelligible) acoustic speech. We observed that the visual cortex exhibited stronger entrainment to the unheard forward acoustic speech envelope compared to the unheard backward acoustic speech envelope. Supporting the notion of a visuo-phonological mapping process, this forward-backward difference of occipital entrainment was not present for actually observed lip movements. Importantly, the respective occipital region received more top-down input especially from left premotor, primary motor, somatosensory regions and, to a lesser extent, also from posterior temporal cortex. Strikingly, across participants, the extent of top-down modulation of visual cortex stemming from these regions partially correlates with the strength of entrainment to absent acoustic forward speech envelope but not to present forward lip movements. Our findings demonstrate that a distributed cortical network, including key dorsal stream auditory regions [3–5], influence how the visual cortex shows sensitivity to the intelligibility of speech while tracking silent lip movements.HighlightsVisual cortex tracks better forward than backward unheard acoustic speech envelopeEffects not “trivially” caused by correlation of visual with acoustic signalStronger top-down control of visual cortex during forward display of lip movementsTop-down influence correlates with visual cortical entrainment effectResults seem to reflect visuo-phonological mapping processes

scholarly journals Community venomics reveals intra-species variations in venom composition of a local population of Vipera kaznakovi in Northeastern Turkey

2018 ◽  
Author(s):  
Daniel Petras ◽  
Benjamin-Florian Hempel ◽  
Bayram Göçmen ◽  
Mert Karis ◽  
Gareth Whiteley ◽  
...  
Keyword(s):  
Snake Venom ◽  
Local Population ◽  
Venom Gland ◽  
Intact Protein ◽  
List Type ◽  
Snake Venoms ◽  
Top Down ◽  
Bottom Up ◽  
Venom Composition ◽  
Snake Bites

AbstractWe report on the variable venom composition of a population of the Caucasus viper (Vipera kaznakovi) in Northeastern Turkey. We applied a combination of venom gland transcriptomics, as well as de-complexing bottom-up and top-down venomics, enabling the comparison of the venom proteomes from multiple individuals. In total, we identified peptides and proteins from 15 toxin families, including snake venom metalloproteinases (svMP; 37.8%), phospholipases A2 (PLA2; 19.0%), snake venom serine proteinases (svSP; 11.5%), C-type lectins (CTL; 6.9%) and cysteine-rich secretory proteins (CRISP; 5.0%), in addition to several low abundant toxin families. Furthermore, we identified intra-species variations of the V. kaznakovi venom composition, and find these were mainly driven by the age of the animals, with lower svSP abundance in juveniles. On a proteoform level, several small molecular weight toxins between 5 and 8 kDa in size, as well as PLA2s, drove the difference between juvenile and adult individuals. This study provides first insights into venom variability of V. kaznakovi and highlights the utility of intact mass profiling for a fast and detailed comparison of snake venoms of individuals from a community.Biological SignificancePopulation level and ontogenetic venom variation (e.g. diet, habitat, sex or age) can cause a loss of antivenom efficacy against snake bites from wide ranging snake populations. The state of the art for the analysis of snake venoms are de-complexing bottom-up proteomics approaches. While useful, these have the significant drawback of being time-consuming and following costly protocols, and consequently are often applied to pooled venom samples. To overcome these shortcomings and to enable rapid and detailed profiling of large numbers of individual venom samples, we integrated an intact protein analysis workflow into a transcriptomics-guided bottom-up approach. The application of this workflow to snake individuals of a local population of V. kaznakovi revealed intra-species variations in venom composition, which are primarily explained by the age of the animals, and highlighted svSP abundance to be one of the molecular drivers for the compositional differences.HighlightsFirst community venomic analysis of a local population of the Caucasian viper (Vipera kaznakovi).The venom gland transcriptome of V. kaznakovi identified 46 toxin genes relating to 15 venom toxin families.Bottom-up venomics revealed the identification of 25 proteins covering 7 toxin families mainly dominated by snake venom metalloproteinases (svMP).Community venomics by top-down mass profiling revealed ontogenetic shifts between juvenile and adult snakes.

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